- #1
BOAS
- 552
- 19
Homework Statement
A spherical capacitor consists of two concentric spherical conductors of radii ##R_{1}## and ##R_2, (R_2 > R_1)##. The space between the two conductors is filled with a linear inhomogeneous dielectric whose relative permittivity varies with the distance ##r## from the centre of the spheres as ##ε_r(r) = (c + r)/r##, with ##c## a constant. The inner sphere carries a total charge ##q## and the outer conductor is grounded.
Using Gauss’s law in dielectrics, compute the electric field (direction and magnitude) at a distance ##R_1 < r < R_2## from the centre of the spheres.
Homework Equations
The Attempt at a Solution
[/B]
I think the charge on the inner sphere ##q##, can be considered the free charge.
Gauss' law in dielectrics;
##\oint \vec D . d\vec a = q##
I don't know the polarisation vector.
##\vec D = \frac{q}{4 \pi R_1^2} \vec r = \epsilon_0 \vec E + \vec P####\vec D = \epsilon_r \epsilon_0 \vec E##
where ##\epsilon_r = \frac{\epsilon}{\epsilon_0}##
##\vec E = \frac{\vec D}{\epsilon_r \epsilon_0}##
I think that this expression gives me the electric field inside the dielectric, but I am concerned that I have not considered the effect of the grounded outer shell.
Do I need to compute the electric displacement inside the outer shell due to the induced charge on it, and the field inside is the linear super position of the two?